Re: [PATCH] drm: bridge: ldb: add support for using channel 1 only

Luca Ceresoli
2023-04-05T07:30:32Z

Hi Marek,

thanks for the quick and detailed review!

On Wed, 5 Apr 2023 05:28:16 +0200
Marek Vasut <marex@denx.de> wrote:

> On 4/4/23 09:37, Luca Ceresoli wrote:
>
> [...]
>
> > @@ -177,28 +183,25 @@ static void fsl_ldb_atomic_enable(struct drm_bridge *bridge,
> > clk_prepare_enable(fsl_ldb->clk);
> >
> > /* Program LDB_CTRL */
> > - reg = LDB_CTRL_CH0_ENABLE;
> > -
> > - if (fsl_ldb->lvds_dual_link)
> > - reg |= LDB_CTRL_CH1_ENABLE | LDB_CTRL_SPLIT_MODE;
> > -
> > - if (lvds_format_24bpp) {
> > - reg |= LDB_CTRL_CH0_DATA_WIDTH;
> > - if (fsl_ldb->lvds_dual_link)
> > - reg |= LDB_CTRL_CH1_DATA_WIDTH;
> > - }
> > -
> > - if (lvds_format_jeida) {
> > - reg |= LDB_CTRL_CH0_BIT_MAPPING;
> > - if (fsl_ldb->lvds_dual_link)
> > - reg |= LDB_CTRL_CH1_BIT_MAPPING;
> > - }
> > -
> > - if (mode->flags & DRM_MODE_FLAG_PVSYNC) {
> > - reg |= LDB_CTRL_DI0_VSYNC_POLARITY;
> > - if (fsl_ldb->lvds_dual_link)
> > - reg |= LDB_CTRL_DI1_VSYNC_POLARITY;
> > - }
> > + reg =
>
> Cosmetic nit, do we need the newline here , can't we just move the first
> '(fsl_ldb->ch0_enabled ? LDB_CTRL_CH0_ENABLE : 0) |' on the same line as
> 'reg =' ? It might need a bit of indent with spaces, but that should be OK.

Sure. Maybe 'reg =<tab>(fsl...' would be even better, it checkpatch
allows.

> > @@ -311,10 +314,23 @@ static int fsl_ldb_probe(struct platform_device *pdev)
> > if (IS_ERR(fsl_ldb->regmap))
> > return PTR_ERR(fsl_ldb->regmap);
> >
> > - /* Locate the panel DT node. */
> > - panel_node = of_graph_get_remote_node(dev->of_node, 1, 0);
> > - if (!panel_node)
> > - return -ENXIO;
> > + /* Locate the remote ports and the panel node */
> > + remote1 = of_graph_get_remote_node(dev->of_node, 1, 0);
> > + remote2 = of_graph_get_remote_node(dev->of_node, 2, 0);
> > + fsl_ldb->ch0_enabled = (remote1 != NULL);
> > + fsl_ldb->ch1_enabled = (remote2 != NULL);
> > + panel_node = of_node_get(remote1 ? remote1 : remote2);
>
> You can even do this without the middle 'remote1' I think:
>
> panel_node = of_node_get(remote1 ? : remote2);

Apparently, but honestly with such short expressions clearly having no
side effects I think it's not helping readability.

> > + of_node_put(remote1);
> > + of_node_put(remote2);
> > +
> > + if (!fsl_ldb->ch0_enabled && !fsl_ldb->ch1_enabled) {
> > + of_node_put(panel_node);
> > + return dev_err_probe(dev, -ENXIO, "No panel node found");
> > + }
> > +
> > + dev_dbg(dev, "Using %s\n",
> > + fsl_ldb_is_dual(fsl_ldb) ? "dual mode" :
>
> I think this is called "dual-link mode" , maybe update the string .

I was using the terms from the NXP docs, but indeed in the kernel it
seems that "dual-link" is the common name. Updating that.

> > @@ -325,20 +341,26 @@ static int fsl_ldb_probe(struct platform_device *pdev)
> > if (IS_ERR(fsl_ldb->panel_bridge))
> > return PTR_ERR(fsl_ldb->panel_bridge);
> >
> > - /* Determine whether this is dual-link configuration */
> > - port1 = of_graph_get_port_by_id(dev->of_node, 1);
> > - port2 = of_graph_get_port_by_id(dev->of_node, 2);
> > - dual_link = drm_of_lvds_get_dual_link_pixel_order(port1, port2);
> > - of_node_put(port1);
> > - of_node_put(port2);
> >
> > - if (dual_link == DRM_LVDS_DUAL_LINK_EVEN_ODD_PIXELS) {
> > - dev_err(dev, "LVDS channel pixel swap not supported.\n");
> > - return -EINVAL;
> > - }
> > + if (fsl_ldb_is_dual(fsl_ldb)) {
> > + struct device_node *port1, *port2;
> > +
> > + port1 = of_graph_get_port_by_id(dev->of_node, 1);
> > + port2 = of_graph_get_port_by_id(dev->of_node, 2);
> > + dual_link = drm_of_lvds_get_dual_link_pixel_order(port1, port2);
> > + of_node_put(port1);
> > + of_node_put(port2);
> >
> > - if (dual_link == DRM_LVDS_DUAL_LINK_ODD_EVEN_PIXELS)
> > - fsl_ldb->lvds_dual_link = true;
> > + if (dual_link < 0)
> > + return dev_err_probe(dev, dual_link,
> > + "Error getting dual link configuration");
>
> Does this need a trailing '\n' in the formatting string or not ? I think
> yes.

Oops, good catch.

> The rest looks good, with the few details fixed:
>
> Reviewed-by: Marek Vasut <marex@denx.de>

Thanks!

--
Luca Ceresoli, Bootlin
Embedded Linux and Kernel engineering